'410 THE HUMAN BODY 



shoot of the lymphatic system; sometimes in the form of a single 

 vessel with a closed dilated end, and sometimes as a network formed 

 by two main vessels with cross-branches. During digestion these 

 lymphatics are filled with a milky-white liquid absorbed from the 

 intestines, and they are accordingly called the lacteals. They com- 

 municate with larger branches in the submucous coat, which end 

 in trunks that pass out through the mesentery to join the main 

 lymphatic system. Finally, in each villus, outside the lacteals and 

 beneath the muscular layer of the villus, is a close network of 

 blood-vessels. 



Opening on the surface of the small intestine, between the bases 

 of the villi, are small glands, the crypts of Lieberkuhn. Each is a 

 simple unbranched tube lined by a layer of columnar cells some of 

 which have a striated free border, though less marked than that on 

 the corresponding cells of the villi, and others are goblet-cells. The 

 crypts of Lieberkuhn are closely packed, side by side, like the 

 glands of the stomach. In the duodenum are found other minute 

 glands, the glands of Brunner. They lie in the submucous coat 

 and send their ducts through the mucous membrane to open on its 

 inner side. 



The Large Intestine (Fig. 136), forming the final portion of the 

 alimentary canal, is about 1.5 meters (5 feet) long, and varies in 

 diameter from about 6 to 4 centimeters (2 to 1 inches). Anato- 

 mists describe it as consisting of the caecum with the vermiform 

 appendix, the colon, and the rectum. The small intestine does not 

 open into the commencement of the large but into its side, some 

 distance from its closed upper end, and the caecum, CC, is that part 

 of the large intestine which extends beyond the communication. 

 From it projects the vermiform appendix, a narrow tube not 

 thicker than a lead pencil, and about 10 centimeters (4 inches) 

 long. The colon commences on the right side of the abdominal 

 cavity where the small intestine communicates with the large, 

 runs up for some way on that side (ascending colon, AC], then 

 crosses the middle line (transverse colon, TC) below the stomach, 

 and turns down (descending colon, DC) on the left side and there 

 makes an S-shaped bend known as the sigmoid flexure, SF; from 

 this the rectum, R, the terminal straight portion of the intestine, 

 proceeds to the anal opening, by which the alimentary canal com- 

 municates with the exterior. In structure the large intestine 



